:root {
  --color-primary: #1A3E6B;
  --color-primary-light: #2A5280;
  --color-secondary: #F5F5F5;
  --color-accent1: #D32F2F;
  --color-accent2: #FFD700;
  --color-neutral1: #8B8682;
  --color-neutral2: #5C7A5A;
  --color-neutral3: #C4A882;
  --color-bg-dark: #0D1B2A;
  --color-text-light: #F5F5F5;
  --color-text-dark: #1A3E6B;
  --color-border-light: rgba(255,255,255,0.15);
  --color-border-rule: #D32F2F;
  --font-heading: Inter, sans-serif;
  --font-body: Noto Sans SC, sans-serif;
  --font-accent: Oswald, sans-serif;
  --fs-heading-xl: clamp(2.5rem, 5vw, 4.5rem);
  --fs-heading-lg: clamp(1.75rem, 3.5vw, 2.75rem);
  --fs-heading-md: clamp(1.25rem, 2.5vw, 1.75rem);
  --fs-body: clamp(0.95rem, 1.2vw, 1.05rem);
  --fs-small: 0.85rem;
  --fs-stat: clamp(1.5rem, 3vw, 2.5rem);
  --lh-body: 1.8;
  --ls-body: 0.05em;
  --ls-heading: -0.5px;
  --fw-heading: 700;
  --fw-body: 400;
  --fw-bold: 600;
  --space-xs: 0.35rem;
  --space-sm: 0.65rem;
  --space-md: 1.25rem;
  --space-lg: 2.5rem;
  --space-xl: 4rem;
  --space-2xl: 6rem;
  --max-width: 1200px;
  --radius-sm: 2px;
  --radius-md: 4px;
  --shadow-card: 0 4px 16px rgba(13,27,42,0.08), 0 1px 4px rgba(13,27,42,0.04);
  --shadow-card-hover: 0 8px 32px rgba(13,27,42,0.14), 0 2px 8px rgba(13,27,42,0.06);
  --transition-fast: 0.2s ease;
  --transition-med: 0.35s ease;
  --transition-slow: 0.5s ease;
  --grid-gap: var(--space-lg);
}

*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: var(--font-body);
  font-size: var(--fs-body);
  line-height: var(--lh-body);
  letter-spacing: var(--ls-body);
  color: var(--color-text-dark);
  background-color: var(--color-secondary);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img {
  display: block;
  max-width: 100%;
  height: auto;
}

a {
  color: inherit;
  text-decoration: none;
  transition: color var(--transition-fast), border-color var(--transition-fast), background var(--transition-fast);
}

a:hover,
a:focus-visible {
  color: var(--color-accent1);
}

a:focus-visible {
  outline: 2px solid var(--color-accent2);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

button {
  cursor: pointer;
  border: none;
  background: none;
  font: inherit;
  color: inherit;
}

button:focus-visible {
  outline: 2px solid var(--color-accent2);
  outline-offset: 2px;
}

ul, ol {
  list-style: none;
}

.skip-link {
  position: absolute;
  top: -100%;
  left: var(--space-md);
  padding: var(--space-sm) var(--space-md);
  background: var(--color-primary);
  color: var(--color-text-light);
  font-weight: var(--fw-bold);
  z-index: 1000;
  border-radius: var(--radius-sm);
  transition: top var(--transition-fast);
}

.skip-link:focus {
  top: var(--space-sm);
}

/* ========== HEADER ========== */
.site-header {
  position: relative;
  width: 100%;
  background: var(--color-primary);
  color: var(--color-text-light);
  box-shadow: 0 2px 12px rgba(13,27,42,0.12);
}

/* 上层品牌说明条 */
.nav-upper {
  background: var(--color-bg-dark);
  padding: var(--space-xs) var(--space-lg);
  border-bottom: 1px solid var(--color-border-light);
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative;
  overflow: hidden;
}

.nav-upper::after {
  content: "";
  position: absolute;
  right: 0;
  top: 0;
  bottom: 0;
  width: 120px;
  background: linear-gradient(135deg, transparent 40%, var(--color-accent2) 40%, var(--color-accent2) 50%, transparent 50%);
  opacity: 0.2;
  pointer-events: none;
}

.brand-statement {
  font-family: var(--font-accent);
  font-size: var(--fs-small);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--color-accent2);
  opacity: 0.92;
  font-weight: 400;
}

/* 下层主导航 */
.nav-lower {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-sm) var(--space-lg);
  position: relative;
  gap: var(--space-md);
}

.site-logo {
  font-family: var(--font-heading);
  font-size: var(--fs-heading-md);
  font-weight: var(--fw-heading);
  font-style: italic;
  letter-spacing: var(--ls-heading);
  color: var(--color-text-light);
  white-space: nowrap;
  border-right: 2px solid var(--color-accent2);
  padding-right: var(--space-md);
  flex-shrink: 0;
}

.site-logo:hover,
.site-logo:focus-visible {
  color: var(--color-accent2);
}

[data-nav] {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
  flex-wrap: wrap;
  justify-content: flex-end;
}

[data-nav] a {
  display: inline-block;
  padding: var(--space-xs) var(--space-sm);
  font-family: var(--font-heading);
  font-size: var(--fs-small);
  font-weight: 500;
  letter-spacing: 0.04em;
  color: var(--color-text-light);
  border-bottom: 2px solid transparent;
  transition: border-color var(--transition-fast), color var(--transition-fast);
  white-space: nowrap;
}

[data-nav] a:hover,
[data-nav] a:focus-visible {
  color: var(--color-accent2);
  border-bottom-color: var(--color-accent2);
}

[data-nav] a[aria-current="page"] {
  color: var(--color-accent2);
  border-bottom-color: var(--color-accent2);
  font-style: italic;
  font-weight: var(--fw-bold);
}

[data-nav-toggle] {
  display: none;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 40px;
  height: 40px;
  background: transparent;
  border: 1px solid var(--color-border-light);
  border-radius: var(--radius-sm);
  padding: 8px;
  gap: 4px;
  transition: border-color var(--transition-fast);
  flex-shrink: 0;
}

[data-nav-toggle]:hover,
[data-nav-toggle]:focus-visible {
  border-color: var(--color-accent2);
}

.hamburger-line {
  display: block;
  width: 100%;
  height: 2px;
  background: var(--color-text-light);
  transition: transform var(--transition-med), opacity var(--transition-med);
  border-radius: 1px;
}

/* 滚动进度条 */
.progress-bar-wrap {
  height: 3px;
  background: var(--color-border-light);
  position: relative;
  overflow: hidden;
}

.progress-bar-fill {
  height: 100%;
  width: 0%;
  background: linear-gradient(90deg, var(--color-accent2), var(--color-accent1));
  transition: width 0.1s linear;
  will-change: width;
}

/* ========== FOOTER ========== */
.site-footer {
  background: var(--color-bg-dark);
  color: var(--color-text-light);
  padding: var(--space-xl) var(--space-lg) var(--space-lg);
  border-top: 2px solid var(--color-accent2);
  position: relative;
  overflow: hidden;
}

.site-footer::before {
  content: "";
  position: absolute;
  left: 0;
  bottom: 0;
  width: 100%;
  height: 4px;
  background: linear-gradient(90deg, var(--color-accent2), var(--color-accent1), var(--color-accent2));
  opacity: 0.3;
}

.footer-content {
  max-width: var(--max-width);
  margin: 0 auto;
  display: grid;
  grid-template-columns: 2fr 1fr 1.5fr;
  gap: var(--space-lg) var(--space-xl);
  align-items: start;
}

.footer-brand {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.footer-logo {
  font-family: var(--font-heading);
  font-size: var(--fs-heading-md);
  font-weight: var(--fw-heading);
  font-style: italic;
  letter-spacing: var(--ls-heading);
  color: var(--color-accent2);
  display: inline-block;
  width: fit-content;
}

.footer-logo:hover,
.footer-logo:focus-visible {
  color: var(--color-text-light);
}

.footer-tagline {
  font-size: var(--fs-small);
  color: var(--color-neutral3);
  letter-spacing: 0.08em;
  opacity: 0.85;
}

.footer-trust {
  font-size: var(--fs-small);
  color: var(--color-neutral1);
  line-height: 1.6;
  max-width: 36ch;
  margin-top: var(--space-xs);
}

.footer-links {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  padding-top: var(--space-sm);
}

.footer-links a {
  font-family: var(--font-heading);
  font-size: var(--fs-small);
  color: var(--color-text-light);
  padding: var(--space-xs) 0;
  border-bottom: 1px solid transparent;
  width: fit-content;
  letter-spacing: 0.06em;
}

.footer-links a:hover,
.footer-links a:focus-visible {
  color: var(--color-accent2);
  border-bottom-color: var(--color-accent2);
}

.footer-contact {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  padding-top: var(--space-sm);
  font-size: var(--fs-small);
  color: var(--color-neutral3);
  line-height: 1.7;
}

.footer-contact span {
  display: block;
}

.footer-bottom {
  grid-column: 1 / -1;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-top: var(--space-lg);
  margin-top: var(--space-md);
  border-top: 1px solid var(--color-border-light);
  font-size: var(--fs-small);
  color: var(--color-neutral1);
}

.footer-icp {
  letter-spacing: 0.04em;
}

.footer-copyright {
  letter-spacing: 0.04em;
}

/* ========== 通用按钮 ========== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-sm) var(--space-lg);
  font-family: var(--font-heading);
  font-size: var(--fs-small);
  font-weight: var(--fw-bold);
  letter-spacing: 0.06em;
  border-radius: var(--radius-sm);
  border: 2px solid transparent;
  transition: background var(--transition-fast), color var(--transition-fast), border-color var(--transition-fast), box-shadow var(--transition-fast);
  cursor: pointer;
  text-align: center;
}

.btn--primary {
  background: var(--color-primary);
  color: var(--color-text-light);
  border-color: var(--color-primary);
}

.btn--primary:hover,
.btn--primary:focus-visible {
  background: var(--color-primary-light);
  border-color: var(--color-accent2);
  color: var(--color-accent2);
  box-shadow: 0 2px 12px rgba(255,215,0,0.15);
}

.btn--accent {
  background: var(--color-accent1);
  color: var(--color-text-light);
  border-color: var(--color-accent1);
}

.btn--accent:hover,
.btn--accent:focus-visible {
  background: #B71C1C;
  border-color: var(--color-accent2);
  color: var(--color-accent2);
  box-shadow: 0 2px 12px rgba(211,47,47,0.2);
}

.btn--outline {
  background: transparent;
  color: var(--color-primary);
  border-color: var(--color-primary);
}

.btn--outline:hover,
.btn--outline:focus-visible {
  background: var(--color-primary);
  color: var(--color-text-light);
  border-color: var(--color-accent2);
}

/* ========== 面包屑 ========== */
.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-xs);
  font-size: var(--fs-small);
  color: var(--color-neutral1);
  padding: var(--space-sm) 0;
}

.breadcrumb a {
  color: var(--color-primary);
  border-bottom: 1px solid transparent;
}

.breadcrumb a:hover,
.breadcrumb a:focus-visible {
  border-bottom-color: var(--color-primary);
  color: var(--color-accent1);
}

.breadcrumb .sep {
  color: var(--color-neutral1);
  margin: 0 var(--space-xs);
  user-select: none;
}

.breadcrumb [aria-current="page"] {
  color: var(--color-text-dark);
  font-weight: var(--fw-bold);
}

/* ========== 正文容器 ========== */
.main-content {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-lg) var(--space-lg) var(--space-2xl);
}

.content-section {
  margin-bottom: var(--space-2xl);
}

.content-section:last-child {
  margin-bottom: 0;
}

/* ========== 网格系统 ========== */
.grid {
  display: grid;
  gap: var(--grid-gap);
  grid-template-columns: 1fr;
}

.grid--2 {
  grid-template-columns: repeat(2, 1fr);
}

.grid--3 {
  grid-template-columns: repeat(3, 1fr);
}

.grid--4 {
  grid-template-columns: repeat(4, 1fr);
}

/* ========== 卡片 ========== */
.card {
  background: var(--color-secondary);
  border: 1px solid var(--color-neutral3);
  border-radius: var(--radius-sm);
  padding: var(--space-lg);
  box-shadow: var(--shadow-card);
  transition: box-shadow var(--transition-med), transform var(--transition-med);
  position: relative;
  overflow: hidden;
}

.card::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0;
  width: 4px;
  height: 100%;
  background: var(--color-accent2);
  opacity: 0;
  transition: opacity var(--transition-fast);
}

.card:hover {
  box-shadow: var(--shadow-card-hover);
  transform: translateY(-2px);
}

.card:hover::before {
  opacity: 0.6;
}

.card-header {
  font-family: var(--font-heading);
  font-size: var(--fs-heading-md);
  font-weight: var(--fw-heading);
  font-style: italic;
  letter-spacing: var(--ls-heading);
  margin-bottom: var(--space-sm);
  color: var(--color-text-dark);
}

.card-body {
  font-size: var(--fs-body);
  line-height: var(--lh-body);
  color: var(--color-neutral1);
}

/* ========== 章节编号 ========== */
.section-number {
  font-family: var(--font-accent);
  font-size: var(--fs-heading-xl);
  font-weight: var(--fw-bold);
  color: var(--color-accent1);
  opacity: 0.2;
  line-height: 1;
  letter-spacing: -0.03em;
  display: block;
  margin-bottom: var(--space-xs);
}

.section-title {
  font-family: var(--font-heading);
  font-size: var(--fs-heading-lg);
  font-weight: var(--fw-heading);
  font-style: italic;
  letter-spacing: var(--ls-heading);
  color: var(--color-text-dark);
  margin-bottom: var(--space-md);
  position: relative;
}

.section-title::after {
  content: "";
  display: block;
  width: 60px;
  height: 3px;
  background: var(--color-accent1);
  margin-top: var(--space-sm);
}

/* ========== 标签 ========== */
.tag {
  display: inline-block;
  padding: 2px var(--space-sm);
  font-size: var(--fs-small);
  font-family: var(--font-accent);
  font-weight: 500;
  letter-spacing: 0.04em;
  background: var(--color-neutral3);
  color: var(--color-text-dark);
  border-radius: var(--radius-sm);
  border: 1px solid var(--color-neutral1);
}

.tag--highlight {
  background: var(--color-accent2);
  color: var(--color-bg-dark);
  border-color: var(--color-accent2);
}

.tag--sport {
  background: var(--color-accent1);
  color: var(--color-text-light);
  border-color: var(--color-accent1);
}

/* ========== 统计数字 ========== */
.stat-number {
  font-family: var(--font-accent);
  font-size: var(--fs-stat);
  font-weight: var(--fw-bold);
  font-style: italic;
  color: var(--color-accent1);
  line-height: 1.2;
}

.stat-label {
  font-size: var(--fs-small);
  color: var(--color-neutral1);
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

/* ========== 图片容器基础 ========== */
.image-wrapper {
  position: relative;
  overflow: hidden;
  background: var(--color-neutral1);
  aspect-ratio: 16 / 9;
  border-radius: var(--radius-sm);
}

.image-wrapper--portrait {
  aspect-ratio: 3 / 4;
}

.image-wrapper--square {
  aspect-ratio: 1 / 1;
}

.image-wrapper img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform var(--transition-slow);
}

.image-wrapper:hover img {
  transform: scale(1.03);
}

.image-wrapper .image-caption {
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  padding: var(--space-sm) var(--space-md);
  background: linear-gradient(transparent, rgba(13,27,42,0.7));
  color: var(--color-text-light);
  font-size: var(--fs-small);
  letter-spacing: 0.04em;
}

/* ========== 响应式 ========== */
@media (max-width: 1024px) {
  .footer-content {
    grid-template-columns: 1fr 1fr;
    gap: var(--space-lg);
  }
  .footer-bottom {
    grid-column: 1 / -1;
  }
}

@media (max-width: 768px) {
  .nav-upper {
    padding: var(--space-xs) var(--space-md);
  }
  .nav-lower {
    padding: var(--space-sm) var(--space-md);
    flex-wrap: wrap;
  }
  .site-logo {
    font-size: var(--fs-body);
    padding-right: var(--space-sm);
    border-right-width: 1px;
  }
  [data-nav-toggle] {
    display: flex;
  }
  [data-nav] {
    display: none;
    flex-direction: column;
    width: 100%;
    background: var(--color-bg-dark);
    padding: var(--space-md);
    border-top: 1px solid var(--color-border-light);
    gap: var(--space-xs);
    margin-top: var(--space-sm);
  }
  [data-nav][data-open] {
    display: flex;
  }
  [data-nav] a {
    width: 100%;
    padding: var(--space-sm) var(--space-md);
    border-bottom: 1px solid var(--color-border-light);
    text-align: left;
  }
  [data-nav] a[aria-current="page"] {
    border-left: 3px solid var(--color-accent2);
    padding-left: calc(var(--space-md) - 3px);
  }
  .footer-content {
    grid-template-columns: 1fr;
    gap: var(--space-lg);
    text-align: center;
  }
  .footer-brand {
    align-items: center;
  }
  .footer-logo {
    margin: 0 auto;
  }
  .footer-trust {
    max-width: 100%;
  }
  .footer-links {
    align-items: center;
  }
  .footer-links a {
    text-align: center;
  }
  .footer-contact {
    align-items: center;
  }
  .footer-bottom {
    flex-direction: column;
    gap: var(--space-sm);
    text-align: center;
  }
  .grid--2,
  .grid--3,
  .grid--4 {
    grid-template-columns: 1fr;
  }
  .main-content {
    padding: var(--space-md) var(--space-md) var(--space-xl);
  }
  .section-number {
    font-size: var(--fs-heading-lg);
  }
}

@media (max-width: 480px) {
  .nav-lower {
    padding: var(--space-xs) var(--space-sm);
  }
  .site-logo {
    font-size: var(--fs-small);
  }
  .brand-statement {
    font-size: 0.7rem;
    letter-spacing: 0.08em;
  }
  .footer-content {
    gap: var(--space-md);
  }
}

/* ========== 无障碍 ========== */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
  .progress-bar-fill {
    transition: none;
  }
  .card:hover {
    transform: none;
  }
  .image-wrapper img {
    transition: none;
  }
  .image-wrapper:hover img {
    transform: none;
  }
  html {
    scroll-behavior: auto;
  }
}

/* ========== 滚动显现占位 (页面级可使用) ========== */
[data-reveal] {
  opacity: 0;
  transform: translateY(12px);
  transition: opacity 0.5s ease, transform 0.5s ease;
}

[data-reveal].revealed {
  opacity: 1;
  transform: translateY(0);
}

@media (prefers-reduced-motion: reduce) {
  [data-reveal] {
    opacity: 1;
    transform: none;
    transition: none;
  }
}